What is being tested?
This test measures the amount of antibody to double-stranded deoxyribonucleic acid (anti-dsDNA) that may be present in the blood. Anti-dsDNA is an autoantibody, produced when a person's immune system fails to distinguish between "self" and "non-self" cellular components. It mistakenly targets and attacks the body's own genetic material, causing inflammation, tissue damage, and other signs and symptoms that are associated with an autoimmune disorder.
Anti-dsDNA is one of several antinuclear antibodies (ANA), a group of antibodies directed against substances found in the nucleus of cells. While it may be present at a low level with a number of disorders, anti-dsDNA is primarily associated with the autoimmune disorder systemic lupus erythematosus (SLE or Lupus). dsDNA antibodies are occasionally found in people who have no medical problem. SLE can affect the kidneys, joints, blood vessels, skin, heart, lungs, and the brain. Symptoms may include joint pain, rashes, fatigue, and kidney dysfunction. SLE occurs most frequently in women between the ages of 15 to 40 and is more common in non-Caucasians. While no direct cause is known, there may be some genetic predisposition. Certain drugs, chemicals, sunlight, or viral infections may trigger an episode.
One particularly serious complication of SLE is lupus nephritis, a condition characterized by inflammation of the kidneys, which can lead to protein in the urine, high blood pressure, and kidney failure. It occurs when the autoantibodies bind to antigens and become deposited in the kidneys.
How is it used?
The double stranded DNA Ab (dsDNA Ab) test is used in support of a diagnosis of systemic lupus erythematosus (SLE) and distinguishes it from other autoimmune disorders. The test is typically ordered following a positive ANA test in people who have clinical signs that suggest SLE. It may be ordered along with another autoantibody panel associated with SLE, the ENA. Depending upon clinical signs and the doctor's suspicions, additional autoantibodies may be ordered to help distinguish between, and rule out, other autoimmune disorders.
The dsDNA Ab test may be used to monitor disease activity in a person who has been diagnosed with SLE. Those with SLE often have flare-ups where symptoms worsen and then die down. Increased anti-dsDNA levels may be seen prior to and during these flare-ups.
When is it requested?
A dsDNA Ab test is ordered when a person shows signs and symptoms that could be due to SLE AND has had a positive ANA test, especially when the ANA presents as a "homogeneous" or "speckled" fluorescent pattern. (See the article on ANA for more on this.) SLE is strongly associated with a positive ANA, which is seen in almost 100% of SLE cases. However, a positive ANA is seen in many other conditions whereas a positive dsDNA Ab is fairly specific for SLE. Since dsDNA Ab is more specific for ANA, the test will not usually be ordered when the ANA is negative. There are several methods of detection of dsDNA antibodies which have different reliabilities though some patients may only make antibodies detectable by one assay.
Some signs and symptoms of SLE include:
The dsDNA Ab test may be ordered periodically to monitor disease progression or flare-ups in a person who has been diagnosed with SLE. It may be repeated when an initial test result is negative but clinical signs and symptoms persist.
What does the result mean?
The result of an dsDNA Ab test is usually considered together with a person's medical history, signs and symptoms, and results of other autoantibody tests.
A high level of anti-dsDNA is strongly associated with SLE and is often significantly increased during or just prior to an SLE flare-up. If the dsDNA Ab test is positive and the person tested has other clinical signs associated with SLE, then is it likely that she has SLE. This is especially true if an anti-Sm test is also positive. In Australia, the anti-Sm test is very rarely positive (less than 5% of SLE patients).
A very low level of anti-dsDNA is considered negative but does not exclude a diagnosis of SLE. Only about 50-60% of those with SLE will have anti-dsDNA measured by one assay, though when assays are combined, up to 80% and perhaps with three or four different assays, 100% of SLE patients may be positive. Low to moderate levels of the autoantibody may be seen with other autoimmune disorders, such as Sjögren syndrome and mixed connective tissue disease (MCTD) and may be induced by some drugs such as TNF inhibitors. dsDNA Ab tests are semi-quantitative and may be performed using different assays. Many laboratories use an dsDNA Ab radioimmunoassay though more modern enzyme immunoassays are as reliable if not better. Many ELISA tests are not completely reliable.
Is there anything else I should know?
Anti-dsDNA is sometimes present with diseases such as chronic hepatitis, primary biliary cirrhosis, and infectious mononucleosis. It may also be seen in those taking drugs such as procainamide and hydralazine. It is not usually tested or monitored under these conditions.
In addition to testing for double stranded DNA antibodies (anti-dsDNA), there is also an anti-single-stranded DNA test. This autoantibody is less commonly tested and is not strongly associated with SLE but may be seen with other autoimmune disorders.
A doctor must rely not only on test results, but on clinical symptoms and the person's history for diagnosis. Symptoms may be nonspecific and often come and go. Test results may not initially be positive for these autoantibodies due to the cyclic nature of autoimmune disorders. In some cases, it may take months or years to show a pattern that might suggest SLE or any of the other autoimmune diseases.
There is no cure for SLE, but the symptoms and complications can be managed. Most people with the condition will experience flare-ups, but most will also have periods of few or mild symptoms.
No, once the autoantibody has been produced by the body, it will continue to be present. However, the concentration in the blood will vary over time and can be present at very low levels.
Autoantibodies do not respond to lifestyle changes because they reflect the presence and activity of an autoimmune process.
The test requires specialised equipment. Your sample will need to be sent to a laboratory that performs these tests.
Autoantibody testing is only necessary when a person shows symptoms that suggest an autoimmune disorder. Most people will never need to have an dsDNA Ab test performed.
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